Hi, Am 12.01.2015 um 01:35 schrieb Linda A. Walsh: > I don't know how it interacts in the case you have setup, but > oflag=direct usually has 'dd' writing to the physical device -- not any > system > cache. I don't know if lvm's cache changes that behavior, but you might > try it w/o the direct flag? I tried it without the flag but now its even worse. I got ~33MB/s (slow drive normally performs 100MB/s and fast drive ~450MB/s). I understand that 'dd' is not the normal use scenario of a disk. But why does the caching (with the tunables I set) is making a difference here? I would expect that with x_threshold and x_adjustment set to 0 there is no difference between normal fs use and dd. I read this written by Joe Thornber in this mailing list a few days ago: > In writeback mode: > > if block is on ssd > write to ssd, complete bio once written > increment write hit counter > else > write to origin and complete > increment write miss counter This would explain why I do not see any write hits. I only got increasing write misses by writing to the drive (even when writing again to the same blocks). Is there an option to influence the algorithm? _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
